Color all of my models using one texture
Just create a new material and assign it to all faces.
Make it uses the desired texture as diffuse or whatever channel suits you.

Then part by part select the faces of your mesh and unwrap them using any simple method with U > Unwrap

In the UV/Image Editor scale down the islands so they fit totally inside one of the nine color cells.

Repeat until you are done. You can readjust them easily by moving each island individually over a desired color.